Dynaco SCA 35
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mhardy6647
Lunatic Member
It is good. The ST-35 (stereo power amp only) is even better; probably (well, arguably) the overall best-sounding piece of Dyna gear "as is".
The value is in the power amp section; more specifically the output iron.
There are many suppliers of replacement and upgrades for the PCBs and power supply.
The value is in the power amp section; more specifically the output iron.
There are many suppliers of replacement and upgrades for the PCBs and power supply.
Binski99
Active Member
I am getting one off of ebay and I have heard from many people that replaceing the tubes enhances the sound. What tubes would be the best for it. It currently has four Dynaco 6bq5 tubes as well as the two 7199 tubes. The two 12ax7 tubes are GE brand.
I am new to tube amps so any advice is appreciated.
I am new to tube amps so any advice is appreciated.
Marantz 500
Active Member
A very good amp, especially since you can get it rather cheaply. Warm, lovely sound, you can play it at nearly full volume without discomfort. Very soft clipping. Best used with fairly efficient speakers though, it's only 17,5 watts per channel. I've had two SCA35 amps, and now I have an ST-35 power amp. To me they sound about the same, I think the SCA35 is a great find! I regret selling the two I had. The original Dynaco labelled tubes should be very high quality, it depends on how much they've been used. If they're due for replacement, newer tubes willl sound better because they're unused, not because they're better quality.
JonL
Lunatic Member
The 12AX7s will probably last about forever. The 7199s should only be replaced with NOS tubes. I've got RCA's in my SCA-35 now. I tried Sovteks (a number of years ago) and they caused a horrible oscillation during warm up. I don't have an opinion on the 6BQ5's, but many small vintage amps use them and I'm sure others will chime in here or you can search the forum as I'm sure it's been discussed before. I test my tubes with a Hickock tube tester that I own. I don't know what to suggest as far as you testing your tubes.
BTW, I built mine from a kit way back in around 1973. It's been my main amp ever since, although it's been in storage for years at a time during certain periods of my life. I've upgraded the filter caps and some of the signal caps, and that's about it in 35 years. It's been a great sounding, reliable amp.
Congratulations on your purchase, and good luck!
BTW, I built mine from a kit way back in around 1973. It's been my main amp ever since, although it's been in storage for years at a time during certain periods of my life. I've upgraded the filter caps and some of the signal caps, and that's about it in 35 years. It's been a great sounding, reliable amp.
Congratulations on your purchase, and good luck!
mhardy6647
Lunatic Member
As long as the EL84s (6BQ5s) that are in there are good, don't replace 'em. You'll be able to hear if there not good.
Brian
An Old Geezer
Are they any good? I dunno but, when I decided to cycle out it and the FM-3 tuner were the only tube pieces I could not part with. Had not problem selling of ARC stuff and Sherwood as well as Fisher but, I could not pry my fingers off the SCA-35 so decided to keep the tuner also.
I'd be more concerned about heat, poor build quality and out of spec parts. These amps run HOT! They will cook the boards. You need to look for blackened pcb. If there is there are replacement glas boards and stuffing them with new components should be easy and not that expensive. You may want to relocate the power transformer or at least get a mufin fan to move air. The amp should have been built of a much bigger chassis.
A point of contention revolves around the 7199 tubes. There is a lot of discussion out there as to them being a poor choice. They are also used in the ST-70. I've found no problems with them and see no reason modding the unit to use another tube. I would consider reconfiguring the slector to delete the tape head input and special input and convert them to additional hi-level inputs, it would require a new selector switch. There also is discussion about deleting the tone controls but there does not seem to be consenus as the best way to do it of if it can be done correctly.
It is a definite keeper but do make sure you go through it well to make sure it is in spec.
I'd be more concerned about heat, poor build quality and out of spec parts. These amps run HOT! They will cook the boards. You need to look for blackened pcb. If there is there are replacement glas boards and stuffing them with new components should be easy and not that expensive. You may want to relocate the power transformer or at least get a mufin fan to move air. The amp should have been built of a much bigger chassis.
A point of contention revolves around the 7199 tubes. There is a lot of discussion out there as to them being a poor choice. They are also used in the ST-70. I've found no problems with them and see no reason modding the unit to use another tube. I would consider reconfiguring the slector to delete the tape head input and special input and convert them to additional hi-level inputs, it would require a new selector switch. There also is discussion about deleting the tone controls but there does not seem to be consenus as the best way to do it of if it can be done correctly.
It is a definite keeper but do make sure you go through it well to make sure it is in spec.
IMO, the SCA-35 is a great little amp provided you have reasonably efficient speakers and don't like to play at rock-concert volumes. I've had two of them...wish I still had one but no need for it really.
The only thing I would do (after making sure the controls are all cleaned, resistors/capacitors are in spec, and tubes are good) is to do the tone control bypass mod which uses the (IMO useless) filter switch as a tone in/out switch. I feel the need for tone controls every so often but the amp generally sounds better without them. If you're interested ping me and I can provide you with step-by-step instructions. (In fact, I may have already posted them here -- can't remember; do a search on my userID and see if so inclined.)
Also, I agree with the muffin fan recommendation above. The power tranny on the SCA-35 runs HOT.
Joe
The only thing I would do (after making sure the controls are all cleaned, resistors/capacitors are in spec, and tubes are good) is to do the tone control bypass mod which uses the (IMO useless) filter switch as a tone in/out switch. I feel the need for tone controls every so often but the amp generally sounds better without them. If you're interested ping me and I can provide you with step-by-step instructions. (In fact, I may have already posted them here -- can't remember; do a search on my userID and see if so inclined.)
Also, I agree with the muffin fan recommendation above. The power tranny on the SCA-35 runs HOT.
Joe
Brian
An Old Geezer
It would depend on how you design the airflow. I've had 2, a rack that the amp sat on and I used them as pushers forcing tghe air from the bottom through to the top and the 2nd was a set of fans over the power transformer and one each over the outputs and used them as pullers. Both worked about the same. What you do not want to do is move the air over the heat generators and then below the chassis. You always want the airflow to start below the heat genrerators and move up.
Brian
An Old Geezer
I would not recommend using the center channel without having loads on the left and right channels for the same reason I'd not run the amp without loads on the outputs, you will probably blow the channel. Us the center channel when you want a center speaker between the left and right speakers to fill in a hole in the middle. If you are using most speakers designed and built in the stereo age, unless you are spinning some very early stereo vinyl you probably will not need it. In them early days they tended to overemphasize the stereo separation and you get left and you'd get right but nothing in between.
Now, the more current use for the center channel would be for a mono speaker in another room.
Now, the more current use for the center channel would be for a mono speaker in another room.
